1. Field of the Invention
The present invention relates generally to an enclosure for interconnecting optical fibers in a fiber optic communications network, and more particularly, to a multi-port optical connection terminal for interconnecting optical fibers of one or more pre-connectorized fiber optic drop cables with optical fibers of a fiber optic distribution cable at a branch point in a fiber optic network.
2. Description of the Related Art
Optical fiber is increasingly being used for a variety of broadband applications including voice, video and data transmissions. As a result of the ever-increasing demand for broadband communications, fiber optic networks typically include a large number of mid-span access locations at which one or more optical fibers are branched from a distribution cable. These mid-span access locations provide a branch point from the distribution cable leading to an end user, commonly referred to as a subscriber, and thus, may be used to extend an “all optical” communications network closer to the subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-premises” (FTTP). Due to the geographical spacing between the service provider and the various subscribers served by each mid-span access location, optical connection terminals, such as closures, network terminals, pedestals, and the like, are needed for interconnecting optical fibers of drop cables extending from the subscribers with optical fibers of the distribution cable extending from the service provider to establish the optical connections necessary to complete the FTTP communications network.
In one example of a fiber optic communications network, one or more drop cables are interconnected with a distribution cable at a mid-span access location within an aerial splice closure suspended from the distribution cable. Substantial expertise and experience are required to configure the optical connections within the closure in the field. In particular, it is often difficult to enter the closure and to identify an optical fiber of the distribution cable to be interconnected with an optical fiber of a particular drop cable. Once identified, the optical fibers of the drop cables are typically joined directly to the optical fibers of the distribution cable at the mid-span access location using conventional splicing techniques, such as fusion splicing. In other instances, the optical fibers of the drop cables and the optical fibers of the distribution cable are first spliced to a short length of optical fiber having an optical connector mounted upon the other end, referred to in the art as a “pigtail.” The pigtails are then routed to opposite sides of a connector adapter sleeve to interconnect the drop cable with the distribution cable. In either case, the process of entering and configuring the aerial splice closure is not only time consuming, but frequently must be accomplished by a highly skilled field technician at significant cost and under field working conditions that are less than ideal. Reconfiguring optical fiber connections in an aerial splice closure is especially difficult, particularly in instances where at least some of the optical fibers of the distribution cable extend uninterrupted through the closure, commonly referred to as a “taut-sheath” or “express” application, since the closure cannot be readily removed from the distribution cable. Further, once the optical connections are made, it is often labor intensive, and therefore costly, to reconfigure the existing optical connections or to add additional optical connections.
In order to reduce costs by permitting less experienced and less skilled technicians to perform mid-span access optical connections and reconfigurations in the field, communications service providers are increasingly pre-engineering new fiber optic networks and demanding factory-prepared interconnection solutions, commonly referred to as “plug-and-play” type systems. Pre-engineered networks, however, require that the location of certain of the branch points in the network be predetermined prior to the distribution cable being deployed. More particularly, pre-engineered solutions require precise location of the factory-prepared mid-span access locations where the preterminated, and sometimes pre-connectorized, optical fibers are made available for interconnection with optical fibers of drop cables extending from the subscriber premises. However, even with arduous pre-engineering it is likely that a factory-prepared mid-span access location will not be positioned exactly as intended when the distribution cable is deployed. For example, when the distribution cable is strung between telephone poles in an aerial deployment, the mid-span access location may actually be positioned farther from the intended location, such as adjacent a telephone pole, than is acceptable for a particular installation. Similarly, when the distribution cable is laid in a buried deployment, the mid-span access location may actually be located someplace other than the intended location, such as at a hand-hole, vault, below-grade closure, network terminal or pedestal. As a result, it may be inconvenient, hazardous or even impossible to make the necessary interconnections between the preterminated or pre-connectorized optical fibers of the distribution cable and the optical fibers of the drop cables at the actual mid-span access location.
Therefore, it would be desirable to provide a multi-port optical connection terminal for interconnecting one or more drop cables with a fiber optic distribution cable at a predetermined branch point in a pre-engineered fiber optic network between a mid-span access location on the distribution cable and a subscriber premises. It would also be desirable to provide a multi-port optical connection terminal that can readily interconnect an optical fiber of at least one pre-connectorized fiber optic drop cable with a respective preterminated or pre-connectorized optical fiber of a fiber optic distribution cable in a pre-engineered fiber optic network. It would also be desirable to provide a multi-port optical connection terminal for installation at a predetermined branch point in a pre-engineered fiber optic network that can be readily reconfigured in the field by a relatively unskilled technician.
Another problem inherent in a fiber optic communications network, especially one in which the drop cables extending from the subscriber premises are buried underground, is the large amount of space required within a standard interconnection enclosure to accomplish both conventional splicing and interconnecting functions. For reasons of both reduced cost and aesthetics, it is desirable to position the interconnection enclosure that interconnects the optical fibers of the drop cables with the optical fibers of the distribution cable within a hand-hole, vault, network terminal or pedestal having the smallest possible volume. At the same time, it is also desirable to limit the number of mid-span access locations required on the distribution cable. Reducing the number of splices and connections performed at each mid-span access location necessarily increases the number of mid-span access locations that must be provided on the distribution cable. Conversely, increasing the number of splices and connections performed at each mid-span access location necessarily increases the required volume of the interconnection enclosure at each mid-span access location and the overall length of the drop cables.
Therefore, it would be desirable to provide a multi-port optical connection terminal for receiving one or more drop cables and interconnecting the drop cables with a fiber optic distribution cable in a fiber optic network that can be positioned within a hand-hole, vault, network terminal or pedestal having the smallest possible volume. It would also be desirable to provide a multi-port optical connection terminal that can readily interconnect an optical fiber of at least one pre-connectorized fiber optic drop cable with a respective optical fiber of a fiber optic distribution cable in a fiber optic network within a hand-hole, vault, network terminal or pedestal having the smallest possible volume. It would also be desirable to provide such a multi-port optical connection terminal for installation in a fiber optic network between a mid-span access location and a subscriber premises that can be readily reconfigured in the filed by a relatively unskilled field technician.